In the book it's explained as 'There's so much bad blood here that whichever one he picks, the other one will try to Murder the Hypotenuse anyway, so might as well have the fight open and aboveboard and over with as quickly as possible'.
Why did Grant decide to shoot Bond several times? The entire plan relied on it looking like he had committed suicide.
Because Grant was a psycho which was the reason Kronsteen's elaborate plan failed.
Besides, he can always make it look like Tatiana was the suicide. Or have Bond's "suicide" be so messy (like jumping off the train into the water or something) that no one gets a good look at the body.
Actually, given Blofeld ordered Klebb specifically to make sure it's painful and humiliating, he might just be following orders.
Are we ever told which of the Gypsy girls get to marry the Prince?
They both spend the night with Bond. Win-win-win! Except for the prince, that is.
My guess is, since the green-clothed one sees Bond off right at the car while the other watches from the porch, it was her.
Why is Kronsteen such a chessmaster? Does it take a member of Mensa to come up with the idea of having a hot girl lure Bond?
That wasn't the plan. The plan was to have a staged defection which the British would suspect as a trap but not suspect that SPECTRE was behind and to ratchet up the tensions between Russian and British intelligence to the point that SPECTRE would never be suspected. This depended on a whole host of people including Tatania, Bond and the various intelligence services being deceived and people acting in exactly the right way, hence why a chessmaster's mind was needed.
Because Hollywood thinks chess players alone are automatically super clever at all other types of thinking.
If MI-6 can so easily get the plans to the Soviet embassy, lay a bomb under its foundations, and walk in on the pretense of wanting a visa...why do they need Tatiana's help to get the LEKTOR at all?
Why not just have Klebb order Tania to hand over the decoding device? As far as she knows, Klebb is still with SMERSH. And remember that in the movie, SPECTRE's main goal is to get the decoding device, the killing of Bond is a bonus(and Kronsteen doesn't bring it up until the end of the briefing). Or at the very least, Blofeld asking why not?(I know I know, "there wouldn't be a movie if they did" but in-universe, this doesn't make sense)
The Lektor is a piece of high grade cryptographic equipment. As such the security regulations are almost bound to be such that NO-ONE would be allowed just to pick up it up and take it away by themselves. At the very least, removing the Lektor from the premises would be a two person job, one more person for SPECTRE to have to fool. It would also have to be very carefully accounted for, even if Tania does take it out of the building, once it doesn’t reach its supposed destination or Tania innocently says ‘oh, Rosa Klebb wanted it’ a widespread security alert will be raised, security codes changed and the Lektor becomes worthless. Sure SPECTRE could maybe come up with a way round this..but why not just let the British do the hard work of planning?